galaxies

Milky Way Regions

Nucleus, Nuclear Bulge, Spiral Arms, Halo

nucleus

Densely packed region with all old stars and a Super--Massive Black hole at the center

2

the nuclear bulge is all old population _ stars

radio

in the nucleus, stars are moving around very rapidly near the center, which is also a strong _____ source.

Spiral Arms

Cold gas and dust along with star formation regions and galactic clusters.

1

spiral arms contain population _ stars

Spiral Arms

_____ ____ have reflection (dust) and emission (H and He gas)

Halo

contains Globular Clusters—all old Population II stars. No interstellar dust and only Hot interstellar gas.

Some solo stars with high inclinations to the galactic plane.

2, hot

The Halo: Globular Clusters—all old Population __ stars. No interstellar dust and only —- interstellar gas.

dark nebulae

Dust—Blocks starlight from more distant stars…

reflection

 Dust—typically reflecting light from nearby hot

young O & B stars—Blue in color

– Scattered Stellar spectra from the nearby star

Emission

Absorbed light from nearby bright stars causes florescence, which results in an _________ Spectrum, typically Red in color due to Hydrogen

Red, Blue

emission: ___ reflection: ____

spiral

The milky way is a ____ galaxy

half

____ of spiral galaxies are barred

hot, red

ellipticals only have ___ interstellar gas, and have ___ old stars

black holes

active galactic nuclei are thought to be due to ____ ____ in their centers

Active Galactic Nuclei

a super bright and compact region at the center of a galaxy powered by a supermassive black hole that is actively pulling in surrounding gas and dust

m87

in the virgo cluster

halo

the ___ contains the earliest objects to form in globular clusters

gravitational lensing

the bending of light by a massive object, causing the light to follow a curved path as if it were passing through a lens. This happens because massive objects warp the fabric of spacetime, and as light travels through this curved spacetime, its path is deflected

5-6

Gravitational Lensing by intermediate galactic clusters

indicates the presence of ___ times more mass than is visible.

radiation

During the earliest times the energy of the Universe was dominated by _________

cosmic microwave background

Temp of universe (4 kelvin)

It shows the variation in densities at that point in time.

• The correlations give strong evidence to

constrain the Universe to be Flat and to

explain the relative contributions of Visible

and Dark Matter and Dark Energy.

drake factors

# Stars in the galaxy, Fraction that are Pop I, Fraction in Habitable

Zone, Fraction with planets, Fraction with terrestrial planets in the

Biosphere. Probability that Life will evolve, probability that the life will

become technological, the Longevity of the technological civilization

large scale structure

the vast patterns of galaxies and matter in the universe, and they are relevant because they help astronomers test cosmological models, probe the nature of gravity and dark matter/energy, and understand the universe's origin and expansion history

GUT (grand unified theories)

rapid inflation of energy until 10^-35 seconds, explains universe flatness

Hubble constant

a measure of the rate at which the universe is expanding. It represents the relationship between a galaxy's distance and its recession velocity, meaning the farther away a galaxy is, the faster it moves away from us

dark energy

By the end of the first second the Matter density (Visible and Dark) began to dominate, and at

about 5 Billion years ago ____ ______ began to dominate and provides the impetus to

make the expansion of the Universe accelerate.